Pick up the Red Gem on your way out! The button on the west side will operate the energy, the other the doors.
Make your way back to the hall between the 2 rooms that we opened. Once done, it is time to get out of this room. There will be a second keyhole in the pillar here too, which will release more enemies again. Once everything is dead, grab the gloves from the section that opened up just north of the gate. Get the Round Key from here too, then move to far south gate and open the gate to the insects, and quickly go back to where we grabbed the round key to prevent getting sandwiched in. Move it to the south east, then place something on the pad in the middle. There is a Red Gem hidden behind another tapestry by the northwest gate. There is only a stone face in this room, so go south, then east.
This will unleash enemies, so be prepared. Just on the other side of the pillar is a hidden keyhole under a tapestry for that key. When you first come down the stairs, go right and snag the Round Key first, then come back to the stairs (since you can't open the gate that way yet) and go through the other gate. You are almost at the end, and in this level you will encounter one of the toughest enemies of the game, that Goromorg!
